The present invention relates to electrophotographic photosensitive materials employed in electrophotographic photoconductors which are used in electrophotographic apparatuses, such as printers, copiers and facsimile machines. The present invention further relates to methods for manufacturing these electrophotographic photosensitive materials and electrophotograhpic photoconductors.
In particular, the invention relates to such photosensitive material and photoconductors that exhibit excellent surface charge retention rate by the use of an improved additive, and to the manufacturing methods of such material and photoconductors.
Electrophotographic photoconductors are required to maintain surface charges in the dark, generate charges upon receipt of light, and transport charges upon receipt of light. Conventional photoconductors include a so-called single-layer type photoconductor having these functions in a single layer, as well as so-called function separated laminated layer type photoconductor, having a layer that mainly serves to generate charges with a layer that serves to maintain surface charges in the dark and to transport charges upon receipt of light.
These conventional photoconductors are used for forming images by known electrophotographic methods, such as the Carlson method. The image formation of this method is performed by charging the photoconductor by a corona discharge in the dark, forming an electrostatic latent image, such as characters or drawings of an original, on the charged surface of the photoconductor, developing the thus formed electrostatic image by means of toner powder, transferring and fixing the toner powder representing the image onto a support, such as paper. After the toner transfer, the residual toner powder is removed, and residual charges are erased by light exposure, so that the photoconductor can be used again.
Several types of photosensitive material for the electrophotographic photoconductor there have been used. Typical materials include selenium, selenium alloys, inorganic photoconductive substances, such as zinc oxide and cadmium oxide, dispersed in a resin binder, as well as organic photoconductive substances, such as poly-N-vinylcarbazole, 9,10-anthracenediole polyester, hydrazone, stylbene, butadiene, benzidine, phthalocyanine or bisazo compound, dispersed in a resin binder or subjected to vacuum deposition or sublimation, for example.
Although utilization of a phthalimide salt in electrophotographic technology is disclosed in Japanese Unexamined Patent Application Publication Nos. S58-211161, H2-272461 and H4-294368, and U.S. Pat. Nos. 5,514,505 and 5,563,014, these references relate only to toners or to agents for giving transparency.
As described above, numerous researches have been made on the electrophotographic photosensitive material, electrophotographic photoconductors, and the methods for manufacturing thereof. However, satisfactory retention rate of surface charge has not yet been achieved.
It is an object of the presetn invention to provide an electrophotographic photosensitve material that overcomes the foregoing problems.
More specifically, it is an object of the present invention to provide electrophotographic photosensitive material that exhibits excellent surface charge retention rate.
It is a further object of the present invention to provide an electrophotographic photoconductor including such photosensitive material.
It is another object of the present invetion to provide a method for manufacturing such photosensitive material and for manufacturing such a photoconductor.
The present invention has been made by studying influence of phthalimide salt to electrophotographic properties. The inventors of the present invention have made numerous researches to solve the foregoing problems. It has been found that the surface charge retention rate is substantially improved when a phthalimide salt compound is contained in electrophotographic photosensitive material capable of charge generating function or in a photosensitive layer of a photoconductor including a charge generating substance. The present invention has been accomplished according to this finding.
Therefore, an electrophotographic photosensitive material of the invention capable of charge generation is characterized by containment of phthalimide salt compound therein.
An electrophotographic photoconductor of the invention comprises an electrically conductive substrate and a photosensitive layer including a charge generation substance on the substrate. The photosensitive layer contains a phthalimide salt compound.
A method of the invention for manufacturing electrophotographic photosensitive material includes a step for adding a phthalimide compound to a charge generation substance or a step for generating a phthalimide salt compound by treating a phthalocyanine compound with a basic compound.
A method of the invention for manufacturing an electrophotographic photoconductor comprises a step for forming a photosensitive layer by coating an electrically conductive substrate with coating liquid including electrophotographic photosensitive material that contains a phthalimide salt compound.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.